Voltage control device



July l 1941. L KAMENARovlc 2,247-,841

VOLTAGE CONTROL DEVICE Filed June 14, 1938 l /Zl'lllllllllllllllllj l Patented July 1, 1941 VOLTAGE CONTROL DEVICE Leone Kamenarovi, Milan, Italy, assignor to Fabbrica Italiana Magneti Marelli Societ Anonima, Milan, Italy, a corporation of Italy Application June 14, 1938, Serial No. 213,715 In Italy June 18, 1937 (Cl. 20L-48) 2 Claims.

This invention relates to devices for voltage control in electric circuits and is primarily concerned with a device of this class which is particularly adapted for radio receivers operated from primary or secondary batteries.

The device of this invention includes, in addition to means for gradually inserting a resistor into the circuit to be controlled, a member which is influenced by the control means for said resistor in such manner as to be moved into a determined position when said resistor is entirely inserted into the circuit.

Accordingly, by using said member to lock a part adapted to prevent the removal of the supply battery, the result is that an exhausted battery Y may be removed and a fresh or charged battery substituted therefor only when said resistor has been entirely inserted into the circuit.

In this manner any possibility of injury to the circuit elements is obviated.

An embodiment of the device of this invention is shown by way of example in the single figure of the annexed drawing, said figure illustrating the device in section and inserted in a circuit which includes a battery, ilaments to be operated therefrom, and a voltage meter and a switch therefor, these several parts being shown diagrammatically.

The device includes a casing I of conducting material in which an insulating former 2 is mounted and carries a resistor wire 3 coiled thereon; said wire 3 having one end connected with an insulated terminal 4 which in turn is connected with one terminal of a battery 5 whose opposite terminal is connected to one end of each of filaments 6. The opposite ends of said filaments and said casing I are also grounded as shown diagrammatically on the drawing.

A screwthreaded hollow spindle 1 is mounted to rotate in the ca-sing I and a nut 8 is mounted on the spindle. The said nut 8 carries a brush 9 adapted to move along and in contact with said coiled resistor wire 3 and has an arm I0 slidably embracing a rod II secured to the casing I to prevent said nut 8 from rotating. The brush 9 is grounded through conducting nut 8, spindle 'I and casing I. A ste-m I2 extends through said hollow spindle I and carries a manipulating knob I3 at one end. To effect engagement of the knob I3 with the spindle "I, this latter has a resilient arm I4 fast therewith and arranged to frictionally engage the opposed surface of the knob I3.

A blade spring I5 is mounted on an extension IB of the casing I and has its end in engagement with the end of the stem I2 opposed to the end thereof which carries the knob I3, said spring acting to hold the knob I3 normally spaced from the resilient arm I4. A second blade spring II is mounted on the extension I6 and is insulated therefrom, cooperating contacts I8, I9 being located on springs I5 and Il. The blade springs I5, I'I are secured to casing extension I6 by means of screws 20 and insulating parts 2I.

lThe adjustment of springs I5, Il is such that their contacts I8, I9 are spaced from each other when the spring I5 has its normal configuration and position in which it holds the stem I2 and knob I3 in a longitudinal position with the knob I3 disengaged from arm I4 of spindle l.

A voltage meter 22 is in circuit across the lead 23 connecting the battery 5 with filaments 6 and the insulated contact spring I'I.

The rod II extending in the casing I parallel with the spindle 'I is mounted to move longitudinally thereof in the casing I and its end portion II adapted to engage a part 24 of a cover (not shown) of a box in which the battery 5 is enclosed. A spring 25 resiliently holds said rod I I, II in the position in which its end portion I I engages said part 24.

Said rod II also carries a linger II" arranged in the path of the nut 8 and adapted to be shifted by said nut 8 when this latter reaches the lower end of its movement along the spindle 'I.

The screw threads of the spindle 'I and nut 8 preferably have a very short pitch so that a very short displacement of the nut 8 and brush 9 is caused by each revolution of the spindle l, this arrangement making the voltage adjustment and brush 9. The said manipulation causes the spring I5 to carry its contact I8 into engagement with contact I9 of the spring I'I and thus the meter is inserted in circuit across the battery 5 and ground at the time the device is manipulated.

A reading of the battery voltage is thus secured each time a manipulation is started and such a reading continues throughout the entire operation, while the meter 22 is automatically out out of the battery circuit during the time the device is not manipulated, to avoid undue consumption of energy from the battery 5 Having in mind that the battery voltage is decreasing during the time of operation of the set, the manipulation of the device consists in causing the brush 9 to move gradually towards the end of resistor wire 3 which is connected with terminal 4 and battery 5 in order to reduce the resistance inserted by the device into the battery circuit. Consequently at the time a fresh battery is required to be substituted for the exhausted one and the resistor 3 is substantially out of circuit, the nut 8 is at the end of its movement spaced from the nger Il or at least this finger is released from said nut 8 owing to the described relationship of parts. Under the above stated conditions, the part 24, which is assumed to be connected with the cover of the battery box, is engaged by the portion l of the rod Il and the operator is prevented from e substituting a fresh battery for the exhausted one.

To replace the exhausted battery by a new one, the operator is required to manipulate the knob E3 and spindle l in a direction to shift the nut 8 and brush 9 towards linger Il" thus causing the full resistor wire 3 to be put into the circuit preparatory to the insertion of a fresh battery in the circuit.

What I claim as my invention and desire to secure by United States Letters Patent is:

l. A rheostat comprising a resistor member, a brush movable with respect to and in contact with said resistor member, means comprising a hollow screw threaded rotatable spindle and a nut engaged with said screw threaded spindle to be reciprocated therealong to actuate said brush, a manipulating knob cooperating with said brush actuating spindle for the drive thereof, a locking member movable to take a retracted and a projecting position to release and engage an associated part, and means biasing said locking member in projecting position, said locking member having a portion which extends in the path of said nut at one end of the stroke thereof for being moved by said nut into retracted position when said nut reaches the said stroke end.

2. A rheostat comprising a resistor member, a brush movable with respect to and in contact with said resistor member, means comprising a hollow screw threaded rotatable spindle and a nut engaged with said screw threaded spindle to be reciprocated therealong to actuate said brush, a stem loose and axially movable Within said hollow spindle, a manipulating knob fast on said stem, la resilient arm fast on said spindle and extending transversely therefrom to frictionally engage the surface of said knob in front thereof when said knob is moved towards said spindle, means biasing said stem and knob into a position with said knob released from said spindle arm, a locking member movable to take a retracted and a projecting position to release and engage an associated part, and means biasing said locking member in projecting position, said locking member having a portion which extends in the path of said nut at one end of the stroke thereof for being moved by said nut into retracted position when said nut reaches the said stroke end.

LEONE KAMENAROVIC. 

